A. Field of the Invention
The present invention relates to apparatus and equipment used in conjunction with patient care in hospitals, convalescent homes and the like. More particularly, the invention relates to sensors for measuring shear and normal forces exerted on body tissues of a seated or recumbent patient.
B. Description of Background Art
Patients in hospitals, nursing homes, and the like, who are required to sit or lie for long periods are thereby subjected to the problem of formation of decubitus ulcers, commonly referred to as bedsores. These result from normal (perpendicular) forces or pressures exerted on areas of the body by a bed or chair, and from tangential or shear forces exerted by different portions of a mattress or cushion supporting a patient. If such forces are exerted on the same parts of a patient's body for sufficiently long periods, body tissues can be broken down, resulting in the formation of painful and sometimes dangerous decubitus ulcers. The deterioration process may be accelerated by such things as poor health, moisture, especially if relatively acidic or alkaline, i.e., having a pH deviating substantially from the pH 7 of pure water, and high temperature. If the conditions causing decubitus ulcers, including high shear forces, are sufficiently great, nasty sores can be caused, which can lead to a lengthy, expensive recovery, medical complications, and even death.
A wide variety of instruments are available for measuring pH, humidity and temperature. Also, the present inventor has developed and is marketing a normal force measurement device for use in monitoring pressures exerted by cushions and mattresses on a patient's body. This device is the Force Sensing Array and is available from Vistamed Corp., P.O. Box 23058, 1315 Pembina Highway, Winnipeg, Manitoba, Canada R3T 5S3. However, the present inventor is unaware of the existence of any devices adapted to measure shear forces exerted in the support of a patient's body by a mattress or cushion, either separately or in combination with normal forces. The present invention was conceived of to fill a perceived need for sensors capable of measuring such forces.